1. Field of the Invention
The invention relates to an indication unit for vehicles, which comprises at least one LED and at least one electrical circuit in a housing. The indication unit is connected to a first controller, which is arranged in the vehicle, and to an LED driver circuit. A second control circuit, which is arranged in or on the housing of the indication unit, operates the LED with pulse-width modulated signals.
Furthermore, it is an object of the invention to propose a process for control of an indication unit, in which the control signals from the vehicle are overlaid with control signals of the indication unit.
2. Description of the Related Art
Indication units on the vehicle are used both inside the vehicle on the dashboard, as well as in or on the interior mirror, but also outside the vehicle, in the field of view of the driver. The mounting position of the exterior mirror or a camera is suitable here. The mirror housing or camera housing, which is already available, can contain different indication units.
Many exterior mirrors comprise an indicator lamp as a typical indication unit, which extends along the front side of the mirror housing in the direction of movement. For road users who are next to or behind the exterior mirror, the indicator lamp can generally not be seen, or only insufficiently. Therefore, additional measures are taken, e.g. using additional LEDs, which radiate along the direction of travel, and are integrated on the outermost edge of the exterior mirror in the indicator.
According to ECE regulations, an additional indicator light in the exterior mirror should illuminate a region beginning from 5° from the longitudinal axis of the vehicle, up to 60° to the longitudinal axis of the vehicle in the opposite direction of movement. The light intensity in this region, which is regulated by law, is defined in the process and must be achieved.
A variety of solutions for indicators in the exterior rear view mirror is known from the prior art. Here, indicator modules are integrated into the housing of an exterior mirror. According to the design, these indicator modules contain fibre optic cables, reflectors, printed circuit boards, lenses and cover glass and illuminants. LEDs are increasingly used as illuminants due to the known advantages.
However, for cost reasons, a simple construction and a reduction of LEDs used is necessary, whereby the light yield must be optimized.
In EP 1120312, an exterior mirror with an indicator is known, which comprises a light module, in which a variety of LEDs shine through openings of a reflector. The LED, which is located on the outermost edge of the exterior mirror, has a radiating direction corresponding to the legal regulations on radiation characteristics. The beam-forming is effectuated by the reflector. The whole light module is clipped into the housing of the exterior mirror, and is electrically contacted by a plug connection.
The wide use of LEDs as a lighting means in a vehicle is known. LEDs are used in front lights and tail lights. In the process, the LEDs can be controlled with pulse-width modulated signals. A dimming effect is achieved by this control, or else the tolerance of the LEDs is compensated in relation to fluctuations in the power supply system of the vehicle. The duty cycle of the signal is significant in the process. The duty cycle is calculated from the switch-on time and the cycle duration of the pulse.
Groups of LEDs are known in DE 102007002809, which are controlled by being pulsed against each other in phases. The reason for this is the implementation of a dimming effect by a duty cycle of approximately 10%, as well as the operation of a variety of LEDs without the occurrence of a flickering effect.
The present invention uses a pulse-width modulation for LEDs, in order to raise the lifespan of the LEDs, on one hand, and on the other hand, in order to exploit an optical effect, which is known as the Broca-Sulzer effect. This effect describes the physiological behavior of the human eye, which perceives short pulses of a certain length as brighter than pulses of a longer length.
DE10260796 shows a control device for the signaling lights of a vehicle. In this publication, the flashing of the different light sources is controlled by a pulse-width modulation. In an example, the bright phase of the indicator is overlaid with a further frequency. Efforts will be made to optimize the optical quality.